Many integrated circuits (ICs) are made up of millions of interconnected devices, such as transistors, resistors, capacitors, and diodes, on a single chip of semiconductor substrate. It is generally desirable that ICs operate as fast as possible, and consume as little power as possible. Semiconductor ICs often include one or more types of memory, such as complementary metal-oxide-semiconductor (CMOS) memory, antifuse memory, and E-fuse memory.
One-time-programmable (“OTP”) memory elements are used in ICs to provide non-volatile memory (“NVM”). Data in NVM are not lost when the IC is turned off. NVM allows an IC manufacturer to store lot number and security data on the IC, for example, and is useful in many other applications. One type of NVM utilizes an electrical fuse (eFuse).
EFuses are usually integrated into semiconductor ICs by using a narrow stripe (commonly also called a “fuse link”) of conducting material (metal, poly-silicon, etc.) between two pads. Applying a program current to the eFuse destroys (i.e., fuses) the link, thus changing the resistivity of the eFuse. This is commonly referred to as “programming” the eFuse. The fuse state (i.e., whether it has been programmed) can be read using a sense circuit.
Like reference symbols in the various drawings indicate like elements.